Sealing end grains,

[Zed]

G'day,

Just went to a place called "the woodworks" in Sydney to buy a blank for my turning class, 2 comments :

1) Geez! blanks are expensive!! ($38 for a 4" thick bit of camphour laurel about 20cm round!)

2) Why is end grain sealed with a waxy substance ? is this to stop it drying out ? if so why ?

I understand that wood is easier to turn if its green but if / when you turn something up and it drys it cracks anyway, so is it not best to just get dry wood and put up with the harder work ?

I've got some nice cypress pine that i'm gunna blank up and use but its still green. When I mentioned this to the instructor he said I should seal the end grain and then I could go for it.. why bother sealing something up if im just gunna turn it straight away anyways ?

I've read in AWR that you should rough turn a green bowl, leave it aside to dry and then finish up when its dry.

Comments anyone ?

[journeyman Mick]

Zed, I'm not a turner but I think the idea of green turning (besides the relative ease) is to reduce the bulk of the timber so it dries faster. The usual rule of thumb is 1" per year so your bit of camphor would take at least 4 years to season (probably longer). So the process is: turn green roughly to size; set aside to dry (some people microwave to accelerate the drying, my brother does this); when seasoned, finish turning. Obviously the idea is to turn it without it splitting, obviously some timbers are going to be more suitable than others, I'm sure there are others out there who will be able to give more/better answers.

Mick

[arose62]

I understand that you seal the end grain because it loses moisture far faster than the rest of the piece. It's this rapid loss that causes the cracking.

By sealing the end grain, the moisture loss is reduced to a gradual process out the 'sides' of the piece, and the wood structure can cope with the gradual stresses without cracking.

Cheers,
Andrew

[river rat]

Zed,
The grain is the tubes that usually run up and down the tree providing a path for sap ( water and nutrients) to run. So by sealing the end grain you slow the process of drying and lessen the chance of cracking conversely if a piece of wood is dry by sealing the end grain you slow down the absorption of moister causing swelling and cracking. I have turned green wood, American red cedar, it was much easier than dry. Tools stayed sharp longer, dust was less although it does spits water at you. We turned it rough let it dry and finished it with minor cracking. The camphour laurel you spoke of is really nice to turn, about as soft as our cedar, pleasing smell a bit over powering when turning and sanding, takes a good finish. I brought back 2 blanks when I was down there in may and wish I could get more. I have heard that the dust can cause problems with the lungs but am not sure. You are lucky there are lots of turners in Oz here there aren't so many so the closest place that sells wood for turning is 150 miles or 4 hours, and for what you got I would have been charged close to $50.00 US, The other options are ordering vie the internet or find logs people cut out of their yards etc.


River Rat